Hydraulic pressure fluid



Patented Dec. 4 1945 HYDRAULIC PRESSURE FLUID Donald L. Katz and Amulf K. Esterer, Ann Arbor, Mich., ,asslgnors to Hydraulic Brake Company, Detroit, Mich., a corporation of California No Drawing. Applicat on May 24, 1943, Serial No. 488,272

1 Claim. (Cl. 252-78) This invention relates to hydraulic pressure fluids, such as brake fluids.

An object of the invention is to provide a fluid having as a main constituent a substance having a substantial lubricating value, due to its viscosity characteristics, and which is in the class of artificial resins polymerized into molecules of considerable size. An important feature relates to using with such a substance a chemical polishing agent capable of smoothing down the microscopic project ons of the metal surfaces in'order to aid in the lubricating eflect.

Other objects are to provide a fluid complying with the present day requirements. and to utilize materials which are on the market or which are known to be readily available.

The resin used in the fluid covered by the present'appllcation is that known commercially as Santolite 3K5," made and sold under that name by Monsanto Chemical Company of 435 North Michigan Avenue, Chicago, Illinois. It is a resinous material formed by aromatic sulfonamides condensed with formaldehyde. Approximately 10.00% of this material is dissolved in approximately 15% of a plasticizer which is not soluble in water, to keep the resin from flocking out in case of contamination of the liquid by taking up water. This may be either of the substances known commercially as Pentaczer 180, and Pentacizer 176, preferably the former. as it has a better viscosity index.- Pentacizer 180 is an ester of pentaerythrit'ol or of dipentaerythritol, which may be of the general formula in which R is an ali hatic hydrocarbon derivative. "Pentaczer 176? is pentaerythritcl diacetate dipropionate, with the formula ccim-co-o-crrm-ocm-o co-cm)= Both are made and sold under these names by are used with approximately 5.00% of a chemical polishing agent such as tricresyl phosphate, sold commercially under the name Lindol MP, substantially of the formula O=PE(O-C6H5.CH3)3. This substance has a characteristic polishing action, gradually smoothing down the microscopic projections on the metal surfaces between which the fluid is required to act as a lubricant, by attacking chemically the microscopic projections of metal to form relatively soft compounds which accumulate in the microscopic depressions.

These substances are mixed with a suitable solvent, as, for example, 69.75% of carbitol (monoethyl ether of diethylene glycol, or

HO-CH2CH2-OCHz-CHz-O-C2Hs) and with an inhibitor aiding in the resistance to corrosion by forming acoating on the metal parts. The preferred inhibitor is a mixture conlleyden Chemical Corporation of Union vention, the resin and plasticizer described above sis n of app ately .10%.ot diethanolamine and 5% diamylamine phosphate.

The above-described fluid has a satisfactorily low rate of change of viscosity with temperature changes; it has little effect on rubber: it does not freeze, but forms a clear gel at low temperatures; at F. the meniscus returns to level after four seconds; its boiling point is 377 F.; its stability is such that it does not boil after two hours at 295 F.; its flash point is 220 F.; it mixes with the principal brake fluids already on the market, and the mixtures remain clear down to 40 F.; it has a water tolerance of 18.6% at 74 R; if contaminated with 4% of water it remains clear at ---40 F.: it does not corrode the metals used in brake systems; and its density is 8.999 lbs. per gallon at 69 F.

While the proportions and constituentsoi one fluid which we now regard as most advantageous are given above, it is not our intention to limit the scope of our invention thereby. or otherwise than by the terms of the appended claim.

We claim:

A hydraulic pressure fluid having IBDDI'OXl mately 10.00% of an aryl sultonamide-iormaldehyde resin, approximately 5.00% of tricresyl phosphate, approximately 15% of an ester of pentaerythritol and organic acid, approximately 69.75% or monoethyl ether of diethylene glycol, 

